Electric motors include, for example, an electric motor in which a plurality of permanent magnets is disposed on an inner circumferential surface of a bottomed cylindrical yoke, and an armature is rotatably provided radially inward from the permanent magnets. The armature includes an armature core externally fitted to a rotary shaft, and a commutator having a plurality of segments disposed thereon. A plurality of teeth extending radially outward is provided on the armature core, and a plurality of axially elongated slots is formed between the teeth. Windings are wound around the armature core via the slots. The windings are electrically connected to a segment of the commutator. A brush for supplying the electric power comes into slide contact with each segment. Current is supplied to the windings via the brush.
Here, in order to reduce size of the electric motor and achieve high performance, various techniques have been suggested. For example, there is disclosed a so-called 4-pole 10-slot 10-segment electric motor in which the number of magnetic poles is set to four by providing the four permanent magnets, the number of slots is set to 10 by forming ten teeth in the armature core, and ten segments are provided in the commutator (for example, see Patent Literature 1).
The windings wound around the electric motor are wound over two teeth in a so-called multiple winding method. Moreover, in the electric motor, the segments having the same potential, i.e., two segments facing each other around the rotary shaft, are short-circuited by an equalizer. Thus, it is possible to reduce the number of installations of the brushes to reduce the size of the electric motor, while achieving the high performance of the electric motor.
Further, for example, there is also disclosed a so-called 6-pole 24-slot 24-segment electric motor in which the number of magnetic poles is set to 6 by providing the six permanent magnets, the number of slots is set to 24 by forming the twenty-four teeth in the armature core, and the twenty-four segments are provided in the commutator (e.g., see Patent Literature 2).
The 6-pole 24-slot 24-segment electric motor is equipped with three winding sections which are wound around each of three teeth groups made up of the four teeth a predetermined number of times, a jumper wire which extends from the winding section and is connected to the two segments, a main winding section which continuously has an intermediate jumper wire which connects the adjacent winding sections without being connected to the segment to be connected when each winding section is individually connected to the segment, and an equalizer (a short-circuit member) which connects a predetermined connected segment to which each jumper wire is connected and the segment to which each winding section is to be connected at the same potential. Thus, it is possible to reduce the number of installations of the brushes to reduce the size of the electric motor, while achieving the high performance of the electric motor by providing the multiple poles.